Zipper tape, container provided with zipper tape, and method for manufacturing container provided with zipper tape

ABSTRACT

Provided is a zipper tape including: a first member including a first base strip and a first engagement portion, the first engagement portion protruding from the first base strip; and a second member including a second base strip and a second engagement portion, the second engagement portion protruding from the second base strip and being engageable with the first engagement portion. A minimum gap between the first member and the second member is less than or equal to 1.1 mm, the minimum gap being based on when the first base strip and the second base strip are opposed to each other and the first engagement portion and the second engagement portion are engaged with each other.

TECHNICAL FIELD

The invention relates to a zipper tape, a zipper-tape-equipped container, and a method of manufacturing the zipper-tape-equipped container.

BACKGROUND ART

In a process of bonding a zipper tape to a bag body in manufacturing a zipper-tape-equipped bag, a method has been adopted in which a zipper tape is thermally pressure-bonded while being guided by a metal plate called a plate (or a separator). Patent Literature 1 discloses a technique that prevents a zipper tape from being fusion-bonded to a separator when the zipper tape is heat-sealed to a film. Such a plate generally has a thickness of approximately 1.1 mm or more, and in order to reduce resistance during passage of the plate, the zipper tape has been designed to have a gap of the zipper tape exceeding 1.1 mm.

CITATION LIST Patent Literature(s)

Patent Literature 1: JP 10-297653 A

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

It is desired that a zipper tape be reduced in thickness in view of: prevention of a pinhole caused by a crushing process on an end portion of the zipper tape; and handleability of zipper-tape-equipped bags that have been manufactured and bundled. However, as described above, a gap of the zipper tape, i.e., a gap of the zipper tape based on when engagement portions are engaged with each other, exceeds 1.1 mm due to a restriction on a manufacturing process, which limits the thickness reduction.

Accordingly, an object of the invention is to provide a zipper tape, a zipper-tape-equipped container, and a method of manufacturing the zipper-tape-equipped container, which are able to reduce a thickness of the zipper tape as compared with a typical zipper tape.

Means for Solving the Problem(s)

[1] A zipper tape includes: a first member including a first base strip and a first engagement portion, the first engagement portion protruding from the first base strip; and a second member including a second base strip and a second engagement portion, the second engagement portion protruding from the second base strip and being engageable with the first engagement portion, in which minimum gap between the first member and the second member is less than or equal to 1.1 mm, the minimum gap being based on when the first base strip and the second base strip are opposed to each other and the first engagement portion and the second engagement portion are engaged with each other.

[2] The zipper tape according to [1], in which the first base strip and the second base strip each include a first portion and a second portion, the first portion including a surface from which the first engagement portion or the second engagement portion protrudes, the second portion including a surface on an opposite side to the first engagement portion or the second engagement portion, and a melting point of a first resin composition forming the first portion is higher than a melting point of a second resin composition forming the second portion.

[3] The zipper tape according to [2], in which a main component of the first resin composition is polypropylene, and a main component of the second resin composition is polyethylene.

[4] The zipper tape according to [2] or [3], in which the first portion has a thickness of greater than or equal to 100 μm, the second portion has a thickness of greater than or equal to 5 μm, and the first base strip and the second base strip each have a thickness of greater than or equal 105 μm.

[5] The zipper tape according to any one of [1] to [4], in which the first member includes a first rib provided on a surface on same side as the first engagement portion, the second member includes a second rib provided on a surface on same side as the second engagement portion, and a minimum gap between the first rib and the second rib is less than or equal to 1.1 mm, the minimum gap being based on when the first base strip and the second base strip are opposed to each other and the first engagement portion and the second engagement portion are engaged with each other.

[6] The zipper tape according to any one of [1] to [5], in which the first base strip and the second base strip include respective thick portions, the thick portions each being provided on a surface on an opposite side to the first engagement portion or the second engagement portion.

[7] The zipper tape according to [6], in which the thick portions are each provided with a width smaller than half a width of the first base strip or the second base strip at a location other than an end portion in a width direction of the first base strip or the second base strip.

[8] A zipper-tape-equipped container including: the zipper tape according to any one of [1] to [7]; and a container body having a first surface to which the first base strip is bonded and a second surface to which the second base strip is bonded.

[9] The zipper-tape-equipped container according to [8], in which the first engagement portion is a female engagement portion, and the second engagement portion is a male engagement portion, the zipper tape is disposed in contact with a containing space, the containing space being provided between the first surface and the second surface, and the first base strip is not bonded to the first surface on a side of the containing space relative to the first engagement portion, and is bonded to the first surface on an opposite side to the containing space relative to the first engagement portion.

[10] The zipper-tape-equipped container according to [8] or [9], in which the container body has a bag shape.

[11] A method of manufacturing the zipper-tape-equipped container according to any one of [8] to [10] includes: interposing the zipper tape inside the container body; and respectively bonding, without interposing a plate between the first base strip and the second base strip, the first base strip and the second base strip to the first surface and the second surface.

According to the above aspect of the invention, it is possible to reduce the thickness of the zipper tape as compared with a typical zipper tape. This easily prevents a pinhole caused by, for example, a crushing process to be performed on an end portion of the zipper tape from being generated in the zipper-tape-equipped bag, and also improves handleability of bundled zipper-tape-equipped bags by a height of the bundled zipper-tape-equipped bags being reduced.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view of a zipper-tape-equipped bag including a zipper tape according to an exemplary embodiment of the invention.

FIG. 2 is a diagram for describing a method of measuring a protrusion height of an engagement portion.

FIG. 3 is a cross-sectional view of a typical zipper-tape-equipped bag.

FIG. 4 is a diagram for describing an exemplary arrangement of a base strip.

FIG. 5 is a diagram for describing another exemplary arrangement of the base strip.

FIG. 6 is a diagram for describing still another exemplary arrangement of the base strip.

FIG. 7 is a diagram for describing a further exemplary arrangement of the base strip.

FIG. 8 is a diagram for describing a modification of an exemplary embodiment of the invention.

DESCRIPTION OF EMBODIMENT(S)

The following describes preferred exemplary embodiments of the invention in detail with reference to the accompanying drawings. It is to be noted that, in this description and the accompanying drawings, components that have substantially the same functional configuration are indicated by the same reference signs, and thus redundant description thereof is omitted.

FIG. 1 is a cross-sectional view of a zipper-tape-equipped bag including a zipper tape according to an exemplary embodiment of the invention. The zipper-tape-equipped bag according to the exemplary embodiment includes a first surface 111 and a second surface 112 which configure a bag body, and a zipper tape 120. The zipper tape 120 includes female engagement portions 121A and 121B and a male engagement portion 122 that are engageable to each other, and base strips 123 and 124. In the following explanation, a part including the female engagement portions 121A and 121B and the base strip 123 may also be referred to as a female member 120A (a first member), and a part including the male engagement portion 122 and the base strip 124 may also be referred to as a male member 120B (a second member). FIG. 1 also illustrates seal bars 510 and 520 to be used in manufacturing the zipper-tape-equipped bag. The base strip 123 of the zipper tape 120 is bonded to the first surface 111 of the bag body with use of the seal bar 510, and the base strip 124 of the zipper tape 120 is bonded to the second surface 112 of the bag body with use of the seal bar 520.

In the above-described zipper tape 120, a minimum gap d_(min) between the female member 120A and the male member 120B is less than or equal to 1.1 mm. The minimum gap d_(min) is based on when the base strip 123 and the base strip 124 are opposed to each other and the female engagement portions 121A and 121B and the male engagement portion 122 are engaged with each other. Here, the minimum gap d_(min) is a gap between the female member 120A and the male member 120B measured in a state in which either the female engagement portions 121A and 121B or the male engagement portion 122 are/is in contact with the base strip opposed thereto or all of the female engagement portions 121A, 121B and the male engagement portion 122 are in contact with the base strip opposed thereto. In the illustrated example, the minimum gap d_(min) is measured in a state in which the male engagement portion 122 is in contact with the base strip 124. It is to be noted that, when measuring the minimum gap d_(min), the base strip 123 and the base strip 124 are assumed to be opposed to each other, that is, the base strips 123 and 124 respectively extend along paired reference planes P1 and P2 which are parallel to each other. The minimum gap d_(min) is defined as a distance perpendicular to the reference planes P1 and P2. It is not taken into consideration that the minimum gap d_(min) varies due to bending of the base strips 123 and 124 in parts other than the engagement portions. In a case where a protruding object such as a rib is present on a surface on an engagement portion side of each of the base strips 123 and 124 as in an example to be described below, the minimum gap d_(min) is measured by subtracting a protrusion height of the protruding object from a gap between the base strips 123 and 124. The minimum gap d_(min) is preferably less than or equal to 1.0 mm, more preferably less than or equal to 0.95 mm, still more preferably less than or equal to 0.90 mm, still further more preferably less than or equal to 0.8 mm, yet still further more preferably less than or equal to 0.7 mm, and even still further more preferably less than or equal to 0.6 mm. A lower limit is not particularly limited, and is, for example, 0, and is preferably greater than or equal to 0.01 mm from a viewpoint of facilitating engagement between the engagement portions.

The first surface 111 and the second surface 112 each include, for example, a single-layer or multi-layer thermoplastic resin film. Specifically, a thermoplastic resin may be low density polyethylene (LDPE), linear low density polyethylene (LLDPE), or polypropylene (PP). PP may be a polypropylene homopolymer (HPP), a polypropylene random copolymer (RPP), or a polypropylene block copolymer (BPP). In a case where the bag body includes a multi-layered film, biaxially oriented polypropylene (OPP), biaxially oriented polyethylene terephthalate (OPET), or biaxially oriented nylon (ONy) may be used for a surface base. These are each not limited to a resin derived from a fossil fuel, and may each be an environmentally friendly bioplastic or a combination of the resin derived from the fossil fuel and the bioplastic. Further, the film forming the bag body may include a layer of an inorganic material formed by, for example, vapor-depositing aluminum or layering an aluminum foil.

The zipper tape 120 is an elongated material that is formed, for example, by extrusion molding of a polyolefin resin. The zipper tape 120 is disposed between the first surface 111 and the second surface 112 of the bag body, and is in contact with a containing space. The zipper tape 120 described above includes, for example, a polyolefin resin. More specifically, the zipper tape 120 may include low density polyethylene (LDPE), linear low density polyethylene (LLDPE), or polypropylene (PP). PP may be a polypropylene homopolymer (HPP), a polypropylene random copolymer (RPP), or a polypropylene block copolymer (BPP). These are each not limited to a resin derived from a fossil fuel, and may each be an environmentally friendly bioplastic or a combination of the resin derived from the fossil fuel and the bioplastic. Examples of the bioplastic include bio-polyethylene and bio-polypropylene, each utilizing a plant-derived raw material. Out of the resin compositions forming the zipper tape 120, some may be the bioplastic as described above, or all may be the bioplastic. To the material of the zipper tape 120, a known additive such as a stabilizer, an antioxidant, a lubricant, an antistatic agent, or a colorant may be added as necessary.

FIG. 2 is a diagram for describing a method of measuring the minimum gap between the members of the zipper tape. In the illustrated example, respective thicknesses of the base strips 123 and 124 are each non-uniform in a width direction. Even in such a case, however, it is possible to make the base strips 123 and 124 respectively extended along the paired reference planes P1 and P2 and to measure the minimum gap d_(min) as the distance perpendicular to the reference planes P1 and P2.

Here, in a typical zipper-tape-equipped bag as illustrated in FIG. 3 , base strips 123P and 124P of a zipper tape 120P may be respectively bonded to the first surface 111 and the second surface 112 of the bag body. In such a case, plates (or separators) 530A and 530B each having a thickness d_(p) of at least 1.1 mm or more are interposed between the base strips 123P and 124P of the zipper tape 120 that are interposed inside the bag body. In this case, in order to reduce resistance of the zipper tape 120 while being conveyed, a minimum gap do between the base strip 123P and the base strip 124P based on when the female engagement portions 121A and 121B and the male engagement portion 122 are engaged with each other and the base strips 123P and 124P are pressed against each other is designed to exceed at least 1.1 mm.

In the exemplary embodiment, as illustrated in FIG. 1 , no plate is interposed between the base strips 123 and 124 in a process of respectively bonding the base strips 123 and 124 of the zipper tape 120 to the first surface 111 and the second surface 112 of the bag body. Accordingly, it is possible to set the minimum gap d_(min) between the female member 120A and the male member 120B based on when the female engagement portions 121A and 121B and the male engagement portion 122 are engaged with each other to less than or equal to 1.1 mm, and also to set the minimum gap d_(min) to 0, as described above. However, the lack of plate interposition can create a possibility that the base strip 123 and the base strip 124 may be welded to each other, when the first surface 111 is bonded to the base strip 123 by heat-sealing performed by the seal bar 510 and the second surface 112 is bonded to the base strip 124 by heat-sealing performed by the seal bar 520. To address this, in the exemplary embodiment, the base strip 123 includes a first portion 123A and a second portion 123B including respective resin compositions that differ from each other, and the base strip 124 includes a first portion 124A and a second portion 124B including respective resin compositions that differ from each other. The first portions 123A and 124A each include a surface from which the engagement portion protrudes from the corresponding one of the base strips 123 and 124, and the second portions 123B and 124B each include a surface on an opposite side to the engagement portion. A melting point of a resin composition (a first resin composition) forming each of the first portions 123A and 124A is higher than a melting point of a resin composition (a second resin composition) forming each of the second portions 123B and 124B. It is thus possible to prevent the welding between the base strip 123 and the base strip 124 by, for example, adjusting a temperature of each of the seal bars 510 and 520 in such a manner as to allow a temperature of each of the base strips 123 and 124 during sealing to be lower than the melting point of the first resin composition and higher than the melting point of the second resin composition.

In order to facilitate the temperature adjustment of each of the seal bars 510 and 520 in the above-described example, the melting point of the first resin composition is preferably higher than the melting point of the second resin composition, for example. A temperature difference between the melting points in this case is, for example, greater than or equal to 3 degrees C., preferably greater than or equal to 5 degrees C., more preferably greater than or equal to 10 degrees C., and still more preferably greater than or equal to 15 degrees C. An upper limit of the temperature difference is not particularly limited, and is approximately less than or equal to 90 degrees C. Further, although respective specific components of the first resin composition and the second resin composition are not particularly limited, a main component of the first resin composition may be polypropylene, and a main component of the second resin composition may be polyethylene. In this case, linear low-density polyethylene is preferably used. Here, the main component of the resin composition means a resin component whose content is the largest among resin components included in a single-layer resin composition as a whole or in each layer of a multi-layer resin composition. The invention is not limited to the above examples, and the main component of the first resin composition may be linear low-density polyethylene, and the main component of the second resin composition may be linear low-density polyethylene whose density is further lower than that of linear low-density polyethylene of the first resin composition. Alternatively, the main component of the first resin composition may be polyethylene, and the main component of the second resin composition may be ethylene vinyl acetate (EVA). The melting point of the resin composition (the second resin composition in the above-described example) forming the surface on the opposite side to the engagement portion is preferably lower than or equal to 110 degrees C., more preferably lower than or equal to 105 degrees C., and still more preferably lower than or equal to 100 degrees C. A lower limit of the melting point is not particularly limited, and is generally higher than or equal to 60 degrees C.

Further, the base strip 123 may include a part other than the first portion 123A and the second portion 123B, and the base strip 124 may include a part other than the first portion 124A and the second portion 124B. For example, in the above-described example, each base strip includes two layers, i.e., the first portion and the second portion; however, in another example, each base strip may include three or more layers. For example, a melting point of a resin composition forming each of the female engagement portions 121A and 121B and the male engagement portion 122 is made to be lower than the melting point of the first resin composition, which makes it possible to improve a crushing property of an end portion when making the bag, and to suppress a defect that a leak occurs from an outside due to a pinhole, etc. It is to be noted that the zipper tape 120 is formed, for example, by co-extrusion of the first and second resin compositions. An interface between the first portion 123A and the second portion 123B and an interface between the first portion 124A and the second portion 124B are melted during sealing. Thus, the first portions 123A and 124A are not always clearly distinguishable from second portions 123B and 124B, respectively, after the zipper-tape-equipped bag is manufactured.

It is also possible to prevent the welding between the base strip 123 and the base strip 124 upon the base strip 123 and the base strip 124 being sealed to the first surface 111 and the second surface 112, respectively, by setting respective thicknesses of the first portions 123A and 124A and the second portions 123B and 124B and respective all-layer thicknesses of the base strips 123 and 124 to predetermined ranges as described below.

Specifically, the first portions 123A and 124A each have a thickness of, for example, greater than or equal to 100 μm, preferably greater than or equal to 110 μm, and more preferably greater than or equal to 120 μm. Further, the first portions 123A and 124A each have a thickness of, for example, less than or equal to 600 μm, preferably less than or equal to 350 μm, and more preferably less than or equal to 320 μm. It is to be noted that the thickness of each of the first portions 123A and 124A includes a height of the protruding portion such as a rib to be described later, and does not include the height of each of the engagement portions 121A, 121B, and 122. It is to be noted that the height of the rib is, for example, greater than or equal to 50 μm, preferably greater than or equal to 70 μm, and more preferably greater than or equal to 80 μm. Further, the height of the rib is, for example, less than or equal to 500 μm, preferably less than or equal to 350 μm, and more preferably less than or equal to 200 μm.

The second portions 123B and 124B each have a thickness of, for example, greater than or equal to 5 μm, preferably greater than or equal to 10 μm, and more preferably greater than or equal to 20 μm, from a viewpoint of a sealing property to be described later. Further, the second portions 123B and 124B each have a thickness of, for example, less than or equal to 100 μm, preferably less than or equal to 80 μm, and more preferably less than or equal to 60 μm. It is to be noted that the thickness of each of the second portions 123B and 124B includes a height of the protruding portion such as a thick portion to be described later.

The all-layer thickness of the base strip 123 including the first portion 123A and the second portion 123B and the all-layer thickness of the base strip 124 including the first portion 124A and the second portion 124B are each, for example, greater than or equal to 105 μm, preferably greater than or equal to 110 μm, and more preferably greater than or equal to 120 μm. Further, the all-layer thickness of the base strip 123 including the first portion 123A and the second portion 123B and the all-layer thickness of the base strip 124 including the first portion 124A and the second portion 124B are each, for example, less than or equal to 700 μm, preferably less than or equal to 400 μm, and more preferably less than or equal to 350 μm. It is to be noted that the all-layer thickness of the base strip 123 including the first portion 123A and the second portion 123B and the all-layer thickness of the base strip 124 including the first portion 124A and the second portion 124B each include the height of the protruding portion such as the rib or the thick portion to be described later, and do not include the height of each of the engagement portions 121A, 121B, and 122.

In addition, if no plate is interposed in the process of respectively bonding the base strips 123 and 124 to the first surface 111 and the second surface 112 as described above, the bonding is possibly to become insufficient as compared with the case where the base strip 123 is sandwiched between the seal bar 510 and the plates and the base strip 124 is sandwiched between the seal bar 520 and the plates. This is solvable by, for example, setting the thickness of each of the second portions 123B and 124B that configure respective sealing layers to be within the above-described range, thereby improving the sealing property. Specifically, the second portions 123B and 124B each have a thickness of, for example, greater than or equal to 5 μm, preferably greater than or equal to 10 μm, and more preferably greater than or equal to 20 μm. Further, the second portions 123B and 124B each have a thickness of, for example, less than or equal to 100 μm, preferably less than or equal to 80 μm, and more preferably less than or equal to 60 μm. Thus, even if the temperature of each of the seal bars 510 and 520 is adjusted to a relatively low temperature in such a manner as to allow the temperature of each of the base strips 123 and 124 during sealing to be lower than the melting point of the first resin composition, for example, it is possible to reliably bond the base strips 123 and 124 to the first surface 111 and the second surface 112, respectively.

According to the exemplary embodiment described above, the minimum gap d_(min) between the female member 120A and the male member 120B based on when the female engagement portions 121A and 121B and the male engagement portion 122 are engaged with each other in the zipper tape 120 is less than or equal to 1.1 mm. The thickness of the zipper tape 120 is thus reduced. This makes it easier to prevent a pinhole caused by, for example, a crushing process on the end portion of the zipper tape 120 from being generated in the zipper-tape-equipped bag, and also improves handleability of bundled zipper-tape-equipped bags by a height of the bundled zipper-tape-equipped bags being reduced.

Regarding the engagement portions provided on the zipper tape 120, the female engagement portions 121A and 121B and the male engagement portion 122 are provided in the illustrated example. However, it is to be noted that shapes of the engagement portions are not limited to the illustrated example, and it is possible to employ various shapes of engagement portions of known zipper tapes having a combination of a claw shape, a hook shape, a knob shape, or the like. In addition, although one group of the female engagement portions 121A and 121B and the male engagement portion 122 is provided in the illustrated example, two or more groups of engagement portions may also be provided. In this case: one or more groups of engagement portions each having one shape (for example, a male-female shape) and one or more groups of engagement portions each having another shape (for example, a hook shape) may be disposed; or two or more groups of engagement portions each having one shape (for example, a male-female shape) may be disposed.

FIG. 4 is a diagram for describing an exemplary arrangement of the base strip. Although FIG. 4 only illustrates the male member 120B, of the zipper tape, including the male engagement portion 122 and the base strip 124, it is to be noted that a similar arrangement is also applicable for the female member 120A including the female engagement portions 121A and 121B and the base strip 123. In the example illustrated in FIG. 4 , thick portions 125A and 125B are provided on a surface, of the base strip 124, on an opposite side to the male engagement portion 122. The thick portions are each a part that is provided with a width smaller than half a width of the base strip 124 at a location other than an end portion in a width direction (a horizontal direction in the figure), and that relatively protrudes with respect to a part (denoted by a reference numeral 127) that is not the thick portion. Providing such thick portions stabilizes contact between the base strip 124 and the second surface 112 during sealing, and makes it possible, for example, to perform stable sealing by a lower temperature of each of the seal bars 510 and 520. In addition, ensuring a thickness necessary for the sealing by the thick portion and reducing the thickness of the base strip in the part that is not the thick portion make it possible to reduce an amount of resin in the base strip.

In the example illustrated in FIG. 4 : an inclined surface 128A is provided on each of both sides, in a width direction of the base strip 124, of the thick portion 125A; and an inclined surface 128B is provided on each of both sides, in the width direction of the base strip 124, of the thick portion 125B. Providing the inclined surface 128A on each of both sides of the thick portion 125A and the inclined surface 128B on each of both sides of the thick portion 125B makes it possible to maintain stable contact between the base strip 124 and the second surface 112 during sealing, and to prevent air from remaining in the part (denoted by the reference numeral 127) between the thick portions and bubbles from being generated after the sealing. A groove 126 provided at a top part of the thick portion 125A is utilized as a sign for identifying a direction of the zipper, but is not necessarily provided.

FIGS. 5 and 6 are each a diagram for describing another exemplary arrangement of the base strip. Although FIGS. 5 and 6 each only illustrate the male member 120B, of the zipper tape, including the male engagement portion 122 and the base strip 124, it is to be noted that a similar arrangement is also applicable for the female member 120A including the female engagement portions 121A and 121B and the base strip 123. In the example illustrated in FIG. 5 , thick portions 125A, 125B, 125C, and 125D are provided on the surface, of the base strip 124, on the opposite side to the male engagement portion 122. The thick portions are each a part that is provided at a location other than the end portion of the base strip 124 in the width direction (the horizontal direction in the figure), and that relatively protrudes with respect to the part (denoted by the reference numeral 127) that is not the thick portion. Respective top parts of the thick portions 125A to 125D may be recessed in a dish shape as illustrated in the figure. A protrusion 129 provided between the thick portions 125A and 125B is utilized as a sign for identifying the direction of the zipper, but is not necessarily provided.

In the example illustrated in FIG. 6 , thick portions 125A, 125B, 125C, 125D, and 125E are provided on the surface, of the base strip 124, on the opposite side to the male engagement portion 122. The thick portions are each a part that is provided at a location other than the end portion of the base strip 124 in the width direction (the horizontal direction in the figure), and that relatively protrudes with respect to the part (denoted by the reference numeral 127) that is not the thick portion. Respective top parts of the thick portions 125A to 125E are each flat, unlike in the example illustrated in FIG. 5 . Providing the thick portions as in the above-described examples illustrated in FIGS. 5 and 6 makes it possible to stabilize the contact between the base strip 124 and the second surface 112 during sealing. Providing such thick portions makes it possible to stabilize the contact between the base strip 124 and the second surface 112 during sealing. In addition, ensuring a thickness necessary for the sealing by the thick portion and reducing the thickness of the base strip in the part that is not the thick portion make it possible to reduce an amount of resin in the base strip.

It is to be noted that the configurations of the base strip described above with reference to FIGS. 4 to 6 are each not limited to the zipper tape described as an exemplary embodiment of the invention in which the minimum gap between the female member and the male member based on when the female engagement portion and the male engagement portion are engaged with each other is less than or equal to 1.1 mm, and is applicable to various zipper tapes.

FIG. 7 is a diagram for describing another exemplary arrangement of the base strip. In the example illustrated in FIG. 7 , a rib 221 is provided on a surface, of the base strip 123, on the same side as the female engagement portions 121A and 121B, and a rib 222 is provided on a surface, of the base strip 124, on the same side as the male engagement portion 122. For example, in addition to that the surface, of the base strip, on the side on which the engagement portion is provided includes a resin composition having a high melting point as described above, the ribs 221 and 222 are provided to thereby make it easier to maintain the gap between the base strip 123 and the base strip 124 and to prevent the welding between the base strip 123 and the base strip 124 during heat-sealing. Further, in the illustrated example, a thick portion 223 whose top part is flat is provided on the surface, of the base strip 123, on the same side as the female engagement portions 121A and 121B, and a thick portion 224 that is similar to the thick portion 223 is provided on the surface, of the base strip 124, on the same side as the male engagement portion 122. The thick portions 223 and 224 are each utilized as a sign for identifying the direction of the zipper, but is not necessarily provided. Further, in order to prevent welding at the thick portions 223 and 224, it is preferable to shift respective positions of the thick portions 223 and 224 in a width direction of the zipper tape.

It is to be noted that, in the example of FIG. 7 , a gap between the ribs 221 and 222 based on when the base strip 123 and the base strip 124 are opposed to each other and the female engagement portions 121A and 121B and the male engagement portion 122 are engaged with each other is the minimum gap d_(min) between the female member 120A and the male member 120B. The minimum gap d_(min) is less than or equal to 1.1 mm. A preferred range of the minimum gap d_(min) is similar to that of the example of FIG. 1 .

It is to be noted that, in the example of FIG. 7 , the ribs 221 and 222 are opposed to each other at respective positions that are the same as each other in the width direction (the horizontal direction in the figure) of the zipper tape 120. Thus, a distance between respective top parts of the ribs 221 and 222 is illustrated to be the minimum gap d_(min). The invention is not limited thereto, and, even in a case where the respective positions of the ribs 221 and 222 are shifted from each other in the width direction of the zipper tape 120, for example, the minimum gap d_(min) is calculable by subtracting, from a gap d_(base) between the base strips 123 and 124, a (maximum) protrusion height of the protruding object such as the rib or the thick portion provided on the surface on the side on which the engagement portion is provided, as described above. Specifically, with use of a protrusion height d_(rib1) of the rib 221 and a protrusion height d_(rib2) of the rib 222, the minimum gap d_(min) is calculable by d_(min)=d_(base)−d_(rib1)−d_(rib2).

It is to be noted that, in the exemplary embodiment of the invention, it is possible to set the gap d_(base) between the base strips 123 and 124 to a small value. Thus, for example, in a case where the protruding objects protrude alternately along the width direction of the zipper tape 120, respective values of the protrusion heights d_(rib1) and d_(rib2) of the protruding objects each become close to the gap d_(base). As a result, the value of the minimum gap d_(min) calculated by d_(min)=d_(base)−d_(rib1)−d_(rib2) can be a negative value. In this case, the minimum gap d_(min) is regarded as substantially zero.

FIG. 8 is a diagram for describing a modification of an exemplary embodiment of the invention. In the illustrated example, the zipper tape 120 is disposed in contact with a containing space SP. The containing space SP is provided between the first surface 111 and the second surface 112 of the bag body. The base strip 123 is not bonded to the first surface 111 on a side of the containing space SP relative to the female engagement portions 121A and 121B, and is bonded to the first surface 111 on a side of an opening 101 of the bag body relative to female engagement portions 121A and 121B. The opening 101 is on the opposite side to the containing space SP. In contrast, the base strip 124 is bonded to the second surface 112 on both the side of the containing space SP and the side of the opening 101 relative to the male engagement portion 122. Such a configuration makes it possible to achieve both internal pressure resistance and easy-openability of zipper-tape-equipped bag as described in, for example, International Publication No. WO 2015/005214. The female engagement portions 121A and 121B and the male engagement portion 122 according to the exemplary embodiment of the invention described above may be reduced in size as compared with typical female engagement portions 121A and 121B and a typical male engagement portion 122. In such a case, engagement strength may decrease. It may thus be advantageous to improve the internal pressure resistance by the above-described configuration.

It is to be noted that, although examples are described above in which a container body is a bag body having a bag shape, a zipper-tape-equipped container may be provided by bonding a zipper tape to a container body other than the bag-shaped container body.

EXAMPLES

Next, Examples of the exemplary embodiment will be described. For each of Examples 1 to 4 presented in Table 1 below, a lower limit of a sealing temperature at which the base strip was bondable to the film (i.e., a minimum sealing temperature) and an upper limit of the sealing temperature at which no fusion-bonding occurred between the base strips during sealing (i.e., a maximum sealing temperature) were measured. In each Example: the first portion of the base strip included a resin composition that included 100 mass % of the polypropylene random copolymer (having a density of 900 kg/m³, a melt flow rate (MFR) of 7.0 g/10 min, and a melting point of 132 degrees C.); <<nret>> and the second portion of the base strip included a resin composition that included, as a main component, metallocene linear low-density polyethylene (having a density of 900 kg/m³, a MFR of 4.0 g/10 min, and a melting point of 95 degrees C.).

TABLE 1 Table 1: Thicknesses and sealing temperatures in Examples Minimum Maximum Thickness Of which Thickness sealing sealing of first height of of second temper- temper- portion rib portion ature ature [μm] [μm] [μm] [° C.] [° C.] Example 1 206 104 40 105 125 Example 2 151 — 29 110 110 Example 3 169 — 28 110 115 Example 4 191 — 31 110 125

In Examples above, the minimum sealing temperature was 110 degrees C. in each of Examples 2 to 4 in which the thickness of the second portion was within a range from 28 μm to 31 μm both inclusive, whereas the minimum sealing temperature was 105 degrees C. in Example 1 in which the thickness of the second portion was 40 μm. It is thus considered that the thickness of the second portion is correlated with the sealing property between the second portion and the film. In contrast, in each of Examples 2 to 4, the maximum sealing temperature increased as the thickness of the first portion increased. It is thus apparent that the fusion-bonding between the base strips during sealing is suppressible by increasing the thickness of the first portion and the all-layer thickness of the base strips. Further, the maximum sealing temperature also increased in Example 1 in which the ribs were provided on the respective surfaces, of the base strips, that were opposed to each other. It is thus apparent that the fusion-bonding between the base strips during sealing is also suppressible by providing the ribs.

Preferred exemplary embodiments of the invention have been described above in detail with reference to the accompanying drawings, but the invention is not limited to such exemplary embodiments. It is apparent that a skilled person in the art of the invention can arrive at various alterations and modifications within the scope of the technical idea recited in the appended claims, and it is understood that such alterations and modifications naturally fall within the technical scope of the invention. 

1. A zipper tape comprising: a first member comprising a first base strip and a first engagement portion, the first engagement portion protruding from the first base strip; and a second member comprising a second base strip and a second engagement portion, the second engagement portion protruding from the second base strip and being engageable with the first engagement portion, wherein a minimum gap between the first member and the second member is less than or equal to 1.1 mm, the minimum gap being based on when the first base strip and the second base strip are opposed to each other and the first engagement portion and the second engagement portion are engaged with each other.
 2. The zipper tape according to claim 1, wherein the first base strip and the second base strip each comprise a first portion and a second portion, the first portion including a surface from which the first engagement portion or the second engagement portion protrudes, the second portion including a surface on an opposite side to the first engagement portion or the second engagement portion, and a melting point of a first resin composition forming the first portion is higher than a melting point of a second resin composition forming the second portion.
 3. The zipper tape according to claim 2, wherein a main component of the first resin composition is polypropylene, and a main component of the second resin composition is polyethylene.
 4. The zipper tape according to claim 2, wherein the first portion has a thickness of greater than or equal to 100 μm, the second portion has a thickness of greater than or equal to 5 μm, and the first base strip and the second base strip each have a thickness of greater than or equal 105 μm.
 5. The zipper tape according to claim 1, wherein the first member comprises a first rib provided on a surface on same side as the first engagement portion, the second member comprises a second rib provided on a surface on same side as the second engagement portion, and a minimum gap between the first rib and the second rib is less than or equal to 1.1 mm, the minimum gap being based on when the first base strip and the second base strip are opposed to each other and the first engagement portion and the second engagement portion are engaged with each other.
 6. The zipper tape according to claim 1, wherein the first base strip and the second base strip comprise respective thick portions, the thick portions each being provided on a surface on an opposite side to the first engagement portion or the second engagement portion.
 7. The zipper tape according to claim 6, wherein the thick portions are each provided with a width smaller than half a width of the first base strip or the second base strip at a location other than an end portion in a width direction of the first base strip or the second base strip.
 8. A zipper-tape-equipped container comprising: the zipper tape according to claim 1; and a container body having a first surface to which the first base strip is bonded and a second surface to which the second base strip is bonded.
 9. The zipper-tape-equipped container according to claim 8, wherein the first engagement portion is a female engagement portion, and the second engagement portion is a male engagement portion, the zipper tape is disposed in contact with a containing space, the containing space being provided between the first surface and the second surface, and the first base strip is not bonded to the first surface on a side of the containing space relative to the first engagement portion, and is bonded to the first surface on an opposite side to the containing space relative to the first engagement portion.
 10. The zipper-tape-equipped container according to claim 8, wherein the container body has a bag shape.
 11. A method of manufacturing the zipper-tape-equipped container according to claim 8, the method comprising: interposing the zipper tape inside the container body; and respectively bonding, without interposing a plate between the first base strip and the second base strip, the first base strip and the second base strip to the first surface and the second surface. 